Maven (6)
'maven' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for ace that I've seen before include "Tennis winner" , "unit > of highest quality" , "Unreturnable serve" , "Service that's never returned" , "Good; service; card" .)
(Other definitions for pundit that I've seen before include "An expert or critic in a particular field" , "Sewing instruments" , "Maestro" , "A person of great learning" , "Expert in a particular field, often consulted" .)